The present invention relates to a balance weight receivable in a balance weight groove in turbomachinery, for example, a steam turbine, methods of remotely installing the balance weight in the groove without removal of turbomachinery casing and tools for installing the balance weight within the groove.
In the manufacture of turbomachinery, for example, steam turbines, final balancing of the rotating component is an essential and important step. Also, at several times during the life of a steam turbine, it is usually necessary to rebalance the rotating component. This is typically accomplished by adding weights to the rotors to compensate for the rotational effects of a bowed rotor, missing or modified rotor components such as buckets or covers, or to lower the vibration levels at which the unit is operating. Weight grooves used to balance rotors during manufacture of a turbine conventionally have a T-shaped or dovetail configuration. Access ports through the casing are typically not provided in older turbines. The weights manufactured as original equipment in such turbines are usually dovetail or T-shaped in configuration and require staking to fix the weights to the rotary component. For balance weight grooves that are intended for rebalancing during service, access ports are typically provided through the casings and the balance weights are usually of a screw plug type.
To convert a rotor that had only a factory balance weight provision to one capable of field balancing, it is necessary to increase the volume of material available for the installation of screw-type plug weights by welding. This process was very time-consuming and expensive. Additionally, the welding process, because of the input of heat to the rotor forging, required that the material be stress-relieved after welding. Re-machining of many of the tight fits on the rotor body was also frequently necessary after the welding and stress relief. This process was also expensive as the rotor required removal from the turbine before the necessary machining tools could be utilized to effect the changes. Also, the casing needed to be modified to provide an access port through which field balance weights could be installed in the rotor. Consequently, there is a need to provide a balance weight/groove combination for both factory and field installation, a method of installing the balance weight in the groove and tools for effecting the installation.